1. Field of the Invention
This invention relates to an apparatus for automatically starting, running and stopping an internal combustion engine. More specifically, it relates to an engine controller designed for automotive applications that addresses convenience, safety, and reliability problems inherent in other systems of this nature.
2. Description of the Prior Art
Systems for the automatic starting, running, and stopping of an internal combustion engine have become fairly common in the market place and are used in a variety of applications such as truck refrigeration units, auxiliary electrical power generators, and remote control engine operation. These systems monitor a specific parameter, such as cargo area temperature in the case of refrigerated truck applications, and operate an engine accordingly. Anyone skilled in the art of engine controller design will realize that, for reasons of necessity, automatic engine controllers have in common means for actuating and de-actuating the fuel supply or ignition system, means for engaging the starter until the engine has started, means for stopping an engine if oil pressure or overheat problems develop, and means for activating engine driven accessories once the engine is running. Furthermore, the design of such an engine controller constitutes a relatively trivial task for an engineer versed in the use of electronic timers, electromechanical relays, and engine sensors. Thus, the basic function of automatic engine starting, running, and stopping of an internal combustion engine will be treated as a functional block in the description of this invention.
It is customary to continuously idle a truck engine in long-haul applications in order to maintain a comfortable environmental temperature within the truck sleeper unit when the ambient temperature is not within the comfort range of the driver. This practice lends itself to an ideal application of automatic engine control with the addition of a thermostat within the sleeper. Accordingly, it is an object of this invention to provide an automatic engine starting, running, and stopping system suitable for the desired truck sleeper environmental control application.
One problem associated with automatic engine control systems for trucking applications is the necessity to train drivers in their use. To further compound the problem, many trucking businesses experience a high rate of driver turnover thereby making training a potentially never-ending process. Thus, it is a further object of this invention to provide an automatic engine control system that requires little or no driver training effort.
Another problem associated with automatic engine control systems for trucking applications is the potential for property damage and personal injury. For instance, a vehicle may be automatically started while a mechanic is working on the engine or when the vehicle is in gear. The usual approach to compensate for these liabilities is to employ hood and transmission sensors in order to disable the automatic starting of an engine when the hood is up or the transmission is in gear. While this approach is valid and necessary, it is well-known that the failure mode of any sensor system is not entirely deterministic. Accordingly, it is another object of this invention to provide a fail safe back-up system to accommodate transmission and hood failure mode uncertainties.
Another problem associated with automatic engine control systems for trucking applications is the necessity for reliability since a disabled vehicle results in loss of revenue far exceeding the fuel savings realized by the system. Problems arising that can adversely affect the startability of an engine include: insufficient cranking energy available from the batteries, low ambient temperatures threatening diesel fuel gel, and problems in the starting and charging system. According to the invention, a fail-to-start condition can be avoided by either initiating a start sequence before conditions: become critical or disregarding a shutdown request from the controlling parameter, namely, a truck sleeper unit temperature.
It is well known that when an automotive type battery is discharged and accepting a charge from the engine alternator, the output voltage of the alternator drops in accordance with the amount of charging current supplied to the battery. Thus, it is a further object of this invention to provide means for ignoring a shutdown request from the controlling parameter when the battery is discharged as indicated by a low alternator output voltage level.
It is also well known that the open circuit voltage of a lead-acid type battery is an indication of state of charge. For instance, if 12.6 volts indicates a 100 percent charge, 12.4 volts may indicate a 75 percent charge, and 12.2 volts may indicate a 50 percent charge on a battery. Given that the parasitic loads on an automotive battery are typically very low in current consumption, thereby implying near open circuit conditions, it is a further object of this invention to initiate a start sequence when the vehicle battery state of charge, as indicated by its voltage, falls to 75 percent, for example.
The amount of energy available from a lead-acid type battery can be estimated given battery state of charge and electrolyte temperature. Further, the energy required to crank a given engine at a specified speed is directly related to oil viscosity, a parameter easily estimated with knowledge of oil type and temperature. Experimental data shows that the likelihood of a successful engine start of an operable diesel engine is high when the cranking speed is above a certain critical level, for example, 200 rpm, and very low when the cranking speed is below the critical level. Accordingly, it is a further object for this invention to provide means of estimating the battery energy available using electrolyte temperature sensing means, to provide means for estimating the energy required to crank an engine at a speed sufficiently above the critical level using engine oil temperature sensing means, and to avoid a fail-to-start condition by initiating a start sequence before the estimated energy available from the battery is below the estimated level needed to crank the engine sufficiently faster than the critical speed.
It is a further object of this invention to provide means for measuring cranking speed and to provide means for affectuating or causing a continuous idle condition when the measured cranking speed is near a critical level.
It is also known that diesel fuel has a tendency to gel at low temperatures. The severity of this problem is significantly reduced while an engine is running because agitation generated by engine vibration and fuel recirculation tends to break up gel formations within the fuel delivery system before their size becomes large enough to restrict fuel flow. Thus, it is a further object of this invention to provide means for initiating a start sequence and ignoring a shutdown request from the controlling parameter when the ambient temperature threatens fuel gel.